Method for removal of a deposition from an optical element, lithographic apparatus, and method for manufacturing a device

Abstract

A method of removing a deposition from an optical element of an apparatus. The method includes providing a hydrogen comprising gas in at least a part of the apparatus, providing nitrogen radicals in the part of the apparatus for generating hydrogen radicals from the hydrogen comprising gas, and contacting the optical element with at least part of the hydrogen radicals to removal the deposition.

1 . A method of removing a deposition from an optical element of an apparatus, the method comprising:
 providing a hydrogen comprising gas in at least a part of the apparatus;   providing nitrogen radicals in said part of the apparatus for generating hydrogen radicals from the hydrogen comprising gas; and   contacting the optical element with at least part of the hydrogen radicals to removal said deposition.   
   
   
       2 . A method according to  claim 1 , wherein the deposition comprises one or more elements selected from a group of B, C, Si, Ge and Sn. 
   
   
       3 . A method according to  claim 1 , wherein the nitrogen radicals are generated from a nitrogen comprising gas by a filament, a plasma or a radiation. 
   
   
       4 . A method according to  claim 1 , wherein the hydrogen comprising gas is provided from a source of hydrogen molecules. 
   
   
       5 . A method according to  claim 4 , wherein the source of hydrogen molecules is integrated with a source of nitrogen radicals yielding a hybrid source for providing nitrogen radicals and hydrogen radicals in at least said part of the apparatus. 
   
   
       6 . A method according to  claim 5 , wherein the hybrid source is arranged in a vicinity of the optical element. 
   
   
       7 . A method according to  claim 1 , wherein the apparatus comprises a lithographic apparatus. 
   
   
       8 . A method according to  claim 7 , wherein the optical element is selected from the group consisting of a mirror, a grating, a reticle, and a sensor. 
   
   
       9 . A method according to  claim 8 , wherein the optical element forms part of a grazing incidence collector module. 
   
   
       10 . A method according to  claim 1 , further comprising generating a flow of at least a nitrogen radical containing gas in the atmosphere of the apparatus in a range of about 60-99% of the sound velocity associated with said atmosphere. 
   
   
       11 . A method according to  claim 1 , further comprising providing methane in at least a part of the apparatus. 
   
   
       12 . An apparatus comprising:
 an optical element;   a first inlet configured to provide hydrogen comprising gas in at least part of the apparatus; and   a second inlet configured to provide nitrogen radicals in said part of the apparatus to generate hydrogen radicals from the hydrogen comprising gas.   
   
   
       13 . An apparatus according to  claim 12 , wherein the second inlet forms part of a source of nitrogen radicals, said source being selected from the group consisting of a filament, a plasma, and a radiation. 
   
   
       14 . An apparatus according to  claim 12 , wherein the first inlet forms part of a source of hydrogen molecules, said source being integrated with the source of nitrogen radicals. 
   
   
       15 . An apparatus according to  claim 14 , wherein the apparatus comprises a lithographic apparatus. 
   
   
       16 . An apparatus according to  claim 12 , wherein the optical element is selected from the group consisting of a mirror, a grating, a reticle, and a sensor. 
   
   
       17 . An apparatus according to  claim 12 , wherein at least the source of nitrogen radicals is arranged to generate a flow a nitrogen gas in the atmosphere of the apparatus in a range of about 60%-99% of the sound velocity associated with said atmosphere. 
   
   
       18 . A lithographic apparatus comprising:
 an illumination system comprising a first optical element constructed to condition a radiation beam;   a support constructed to support a patterning device, the patterning device being configured to impart the radiation beam with a pattern in its cross-section to form a patterned radiation beam;   a substrate table constructed to hold a substrate;   a projection system comprising a second optical element configured to project the patterned radiation beam onto a target portion of the substrate;   a hydrogen comprising gas; and   a source of nitrogen radicals arranged to generate hydrogen radicals from the hydrogen comprising gas to remove a deposition from at least a surface of the first optical element and/or the second optical element.   
   
   
       19 . A lithographic apparatus according to  claim 18 , wherein the source of nitrogen radicals is selected from the group consisting of a filament, a plasma, and a radiation. 
   
   
       20 . A lithographic apparatus according to  claim 18 , further comprising a source of a hydrogen comprising gas, said source being integrated with the source of nitrogen radicals. 
   
   
       21 . A lithographic apparatus according to  claim 20 , wherein a gas outlet of the source of hydrogen comprising gas is arranged in a direct vicinity of a gas outlet of the source of nitrogen radicals. 
   
   
       22 . A lithographic apparatus according to  claim 18 , wherein at least the source of nitrogen radicals is arranged in a direct vicinity of the surface to be cleaned. 
   
   
       23 . A lithographic apparatus according to  claim 18 , wherein the first optical element and/or the second optical element are selected from the group consisting of a mirror, a grating, a reticle, and a sensor. 
   
   
       24 . A lithographic apparatus according to  claim 18 , wherein the optical element comprises a Ru surface. 
   
   
       25 . A lithographic apparatus according to  claim 18 , further comprising a source of methane. 
   
   
       26 . A lithographic apparatus according to  claim 18 , wherein the surface is provided with a Si 3 N 4  coating. 
   
   
       27 . A lithographic apparatus according to  claim 18 , wherein the deposition comprises one or more elements selected from the group consisting of B, C, Si, Ge, and Sn. 
   
   
       28 . A lithographic apparatus according to  claim 18 , wherein the illumination system comprises a grazing incidence collector. 
   
   
       29 . A lithographic apparatus according to  claim 18 , wherein at least the source of nitrogen radicals is arranged to generate a flow a nitrogen gas in the atmosphere of the apparatus in a range of about 0.60-0.99 of the sound velocity associated with said atmosphere. 
   
   
       30 . A device manufacturing method comprising:
 projecting a patterned beam of radiation onto a substrate using a lithographic apparatus; and   providing nitrogen radicals in an atmosphere of the lithographic apparatus for interacting with a hydrogen comprising gas present in said atmosphere for generating hydrogen radicals for removing a deposition from a surface of an optical element of the lithographic apparatus.   
   
   
       31 . A device manufacturing method according to  claim 30 , further comprising:
 adding methane to said atmosphere.